Ion source device for ion microanalyzer and the like

ABSTRACT

A pulse voltage generating circuit incorporated in an ion source device of the type so as to supply a pulse voltage to an intermediate electrode of the device thereby to allow discharge to occur in said device with high efficiency.

United States Patent 11 1 Kondo et al.

1111 3,710,266 Jan. 9,1973

54] ION SOURCE DEVICE FOR ION MICROANALYZER AND THE LIKE [75] Inventors: Toshio Kondo, Kokubunji; Hifunii Tamura, Hachioji, both of Japan 731 Assignee: 111mm, 1,111., Tokyo, Japan 22 Filed: Aug.26, 1971 21 Appl.No.: 175,219

[30] Foreign Application Priority Data Aug. 26,1970 Japan ..45 s4401 52 U.S.Cl. ..328/233,250/49.5R,313/63,

5s FieldofSearch ..313/63;'315/111;328/253;

[56] References Cited UNITED STATES PATENTS 3,178,578 4/1965 Gale ..250/49.5 R X 3,290,552 12/1966 Van Ornum 1 ..3 15/1 11 3,458,743 7/1969 Cleland et al.... ..328/233 X 3,494,852 2/1970 Doctoroff ..313/63 X 3,513,351 5/1970 Kelley ..313/63 X Primary Examiner-Alfred L. Brody Attorney-Craig", Antonelli & Hill 57 ABSTRACT A pulse voltage generating circuit incorporated in an ion source device of the type so as to supply a pulse voltage to an intermediate electrode of the device thereby to allow discharge to occur in said device with high efficiency.

5 Claims, 4 Drawing Figures PATENTEDJAH 9197s wzwmmnozg M A i ,m 4 2 OM W 2 Mwm V o m F am am OR \I 2 A m M Q 0 .Emmmno M50585 m F Mm w 01% mwmaiomfi 022.15%

FIG.

ION ACCEL- ERATING SCR ION ACCELER- ATING VOLT- AGE SOURCE QRNEYS ION SOURCE DEVICE FOR ION MICROANALYZER AND THE LIKE BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to an ion source device for an ion microanalyzer and the like and, more particularly, to an ion source device of the Duoplasmatron type provided with means for efficiently starting the same.

2. Description of the Prior Art As is well-known, an ion source device of the Duoplasmatron type is used in an ion microanalyzer.

Hitherto, such an ion source device has been so con structed that a discharge starting voltage is applied to an intermediate electrode thereof through an inter.- mediate electrode resistor so as to startthedischarge which occurs therein. In order to increase the discharge efficiency of said device, the resistance value of saidresistor must be increased so that the discharge starting voltage becomes high. However, in such conventional devices, sincethe resistance value ofthe resistor must be decreased to make the discharge starting voltage low, the discharge efficiency thereof decreases.

Moreover, an additional power source for generating.

the discharge starting voltage, as well as accelerating voltage sources for supplying operation voltages to the intermediate electrode and an anode, must be provided in the conventional devices.

SUMMARY OF THE INVENTION An object of this invention is to provide means for supplying a high discharge starting voltage to theinter.

mediate electrode to which the resistor having ahigh resistance value is normally connected so as to increase the discharge efficiency.

Another object of this invention isto provide anion source device which can be started without any additional power source.

The invention is characterized by provision thereto.

of pulse voltage generating means for supplying a pulse voltage as said discharge starting voltage to the intermediate electrode so as to start the discharge of electrons in said ion source devices a BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 is a schematic diagram indicating a conventional device of the Duoplasmatron type;

FIG. 2 shows the relationshipbetween the ion current or electrode current and resistance value of the ins termediate electrode resistor;

FIG. 3 shows the relationshipbetween the discharge.

starting voltage and said resistance value; and

FIG. 4 is a schematic diagram indicating an embodiment of this invention.

DESCRIPTION OF A PREFERRED EMBODIMENT emitted from said filament.

A magnet 5 made of ferrite is disposed between said intermediate electrode 2 and an anode 3 so as to insulate these elements from each other and to concentrate the electrons in the space therebetween. A gas of a constant quantity is supplied into a space enclosed by said and an extractor 4 so that the ions are extracted downwardly from said extractor 4 and further are introduced. into an ion microanalyzer (not shown), whereby the ions are directed to a specimen (not shown) in a known manner.

In the above device, each factor shown in FIGS. 2 and 3 depends'upon a gas pressure and other operational conditions and the sizes of the ion source device. In FIG. 2, curves a, b, and 0 show an anode current, an intermediate electrode current and an ion current for various resistance values of the intermediate electrode resistor, respectively. As is apparent from said figures, the ion current as well as the anode current increase in response to increase in the resistancevalue of said resistor 7 so that the discharge efficiency is improved, but in this case, the dischargestarting voltage becomes high. On: the other hand, if said resistance value is decreased to make said voltage low, the ion current decreases. Therefore,it is apparent that defects are inherent in the conventional device for the above" reasons.

According to the invention, the above defects can be eliminated by employment of pulse voltage generating means, as shownin FIG. 4, wherein numerals 8 and 9 show said heating power source and said electron accelerating voltage source, respectively. The heating power source 8 comprises a rectifying circuit 14 and a smoothing circuit 14' composed of a choke coil 17, and condensers I5 and 16. The electron accelerating voltage source 9 comprises a rectifying circuit 18 and a smoothingcircuit 18' composed of a choke coil 21 and condensers 19 and 20. The AC power is supplied from an .AC power source 11 to both the rectifying circuits l4.and 18 through transformers 12 and 13.

The output of thesmoothing circuit 18' of said voltage source9-is connected to the intermediate electrode 2 through an intermediate electrode resistor 22 and a diode 23.

There is a pulse voltage, generating circuit 31 which comprises: a triggering circuit composed of a resistor 26, a condenser 27, and a discharge tube 28; a switching element, such as; for example, a silicon controlled rectifier SCR having a gate g, which is triggered by said triggering circuit; a condenser 30 connected to the output of said voltage source 9 through a resistor 24 whose dischargeoperation is controlled by said ele-' ment SCR; and a transformer 25 whose primary winding is connected inseries withthe switching element SCR across the condenser 30 and whose secondary winding is connected in series with. a condenser 29 and inserted between the intermediate electrode 2 and the filament l.

Now, supposing that discharge does not occur in the ion source device and thus the intermediate current does not flow into the intermediate electrode 2, the condenser 30 is charged by the output of the smoothing circuit 18' through the resistor 24 and the condenser 27 is charged through resistors 22 and 26, to thereby increase the terminal voltages thereacross, respectively. When the voltage across the condenser 27 reaches at a certain level which is large enough to cause the discharge tube 28 to discharge, it discharges, so that'a trigger current is supplied to the gate electrode of said switching element SCR and thus it becomes conductive, i.e., it is switched to its ON state. As a result of this, a pulse current flows through the primary winding of the transformer 25 and said element SCR from said condenser 30 due to its discharging. At this time, a pulse high voltage is induced in the secondary winding of the transformer 25 and is applied to the intermediate electrode 2 through a condenser 29.

Therefore, if the pulse voltage is predetermined to have a value equal to that of said discharge starting voltage, discharge can be started and the ion source device begins to operate. In this case, application of the pulse voltage having, a high voltage value to the smoothing circuit 18 is prevented by the diode 23.

When discharge starts in the above manner, the intermediate electrode current flows into the intermediate electrode 2 through the resistor 22, so that the voltage applied to the condenser 27 drops and the terminal voltage thereacross does not reach said certain level. Therefore, since the switching element SCR is not triggered, no pulse voltage is applied to the intermediate electrode 2 during normal operation of the ion source device.

In the device described above, by causing the intermediate electrode resistor 22 to have a sufficient resistance value, the discharge efficiency of said ion source device can be greatly improved. Moreover, the amplitude of the pulse voltage serving as said discharge starting voltage can be varied freely by changing the turn ratio of the transformer 25.

We claim:

1. In an ion source device for an ion microanalyzer and the like comprising a filament for emitting electrons when energized, a heating power source connected to said filament for energizing said filament, an intermediate electrode for accelerating said electrons, an electron accelerating voltage source connected between said filament and said intermediate electrode for supplying therebetween an electron accelerating voltage, an intermediate electrode resistor connected between said electron accelerating voltage source and said intermediate electrode, means for supplying a gas into a space adjacent to said intermediate electrode, an anode for accelerating ions produced in said space, a magnet disposed between said intermediate electrode and said anode for insulating said elements from one another and for concentrating said ions, an extractor for extracting said ions, and an ion accelerating voltage source connected between said anode and said extractor, the improvement which comprises pulse voltage generating means connected in series circuit with said. intermediate electrode and said electron accelerating voltage source for supplying a pulse voltage between said intermediate electrode and said filament only to start discharge in said ion source device. l

. The combination defined in claim 1, wherein said pulse voltage generating means includes a triggering circuit, means for supplying said triggering circuit with a potential obtained by subtraction of the voltage drop across said intermediate electrode resistor from the voltage of the electron accelerating voltage source for operatively generating a trigger voltage when the supplied potential exceeds the discharge starting voltage of said ion source device, a switching element having a gate triggered by the trigger voltage of said triggering circuit, a pulse transformer having primary and secondary coils, and a first condenser connected in parallel with a series circuit of the primary coil of said pulse transformer and said switching element.

3. The combination defined in claim 2, wherein the triggering circuit includes a second condenser connected to the intermediate electrode resistor and a discharge tube connected between said second condenser and the gate of said switching element for initiating its discharge when the voltage across said 

1. In an ion source device for an ion microanalyzer and the like comprising a filament for emitting electrons when energized, a heating power source connected to said filament for energizing said filament, an intermediate electrode for accelerating said electrons, an electron accelerating voltage source connected between said filament and said intermediate electrode for supplying therebetween an electron accelerating voltage, an intermediate electrode resistor connected between said electron accelerating voltage source and said intermediate electrode, means for supplying a gas into a space adjacent to said intermediate electrode, an anode for accelerating ions produced in said space, a magnet disposed between said intermediate electrode and said anode for insulating said elements from one another and for concentrating said ions, an extractor for extracting said ions, and an ion accelerating voltage source connected between said anode and said extractor, the improvement which comprises pulse voltage generating means connected in series circuit with said intermediate electrode and said electron accelerating voltage source for supplying a pulse voltage between said intermediate electrode and said filament only to start discharge in said ion source device.
 2. The combination defined in claim 1, wherein said pulse voltage generating means includes a triggering circuit, means for supplying said triggering circuit with a potential obtained by subtraction of the voltage drop across said intermediate electrode resistor from the voltage of the electron accelerating voltage source for operatively generating a trigger voltage when the supplied potential exceeds the discharge starting voltage of said ion source device, a switching element having a gate triggered by the trigger voltage of said triggering circuit, a pulse transformer having primary and secondary coils, and a first condenser connected in parallel with a series circuit of the primary coil of said pulse transformer and said switching element.
 3. The combination defined in claim 2, wherein the triggering circuit includes a second condenser connected to the intermediate electrode resistor and a discharge tube connected between said second condenser and the gate of said switching element for initiating its discharge when the voltage across said second condenser exceeds the discharge starting voltage.
 4. The combination defined in claim 2, wherein the secondary coil of said pulse transformer is connected between the intermediate electrode and the filament.
 5. The combination defined in claim 1, wherein a diode is connected between said intermediate electrode and said intermediate electrode resistor for preventing application of the pulse voltage from said puLse voltage generating means to said electron accelerating voltage source. 